Interpretive Summary: Invasive species are an extremely big problem in the United States and cost its citizens over $120 billion annually. Saltcedar and giant reed are exotic weeds that invade riparian areas and use excessive amounts of water. Both species occur in dense stands along the Rio Grande in west Texas and have contributed to water shortages in the region. A study was conducted using airborne remote sensing (aerial photography and videography) techniques integrated with global positioning system (GPS) and geographic information system (GIS) technologies for detecting and mapping saltcedar and giant reed infestations along the Rio Grande from near Laredo in south Texas to near El Paso in west Texas. Integration of the GPS with the video imagery permitted latitude-longitude coordinates of weed infestations to be recorded on each image. The GPS coordinates on imagery depicting where saltcedar and giant reed infestations occurred were entered into the GIS. Distribution maps were developed denoting locations where saltcedar and giant reed infestations occurred along the Rio Grande. These findings should be useful to natural resource managers and weed scientists interested in locating noxious weed infestations over large and inaccessible area

Technical Abstract:
The Rio Grande is a major source of water for agricultural and municipal uses in Texas and northern Mexico. Water shortages in the Rio Grande have been significantly impacted by the invasion and spread of the invasive weed species giant reed (Arundo donax L.) and saltcedar (Tamarix chinensis Lour.). Giant reed and saltcedar are wetland species that generally grow adjacent to the river. This paper reports the results of an aerial remote sensing survey conducted in 2002 on the Rio Grande from near Laredo in south Texas to near El Paso in west Texas. Aerial photography and videography were acquired simultaneously of the Rio Grande. Color-infrared photography and videography were used to detect giant reed, whereas conventional color photography and videography were used to distinguish saltcedar. The videography was integrated with global positioning system (GPS) and geographic information system (GIS) technologies for detecting and mapping the distribution of the two weed species. Integration of the GPS with the video imagery permitted latitude-longitude coordinates of weed infestations to be recorded on each image. The GPS coordinates on the video scenes depicting giant reed and saltcedar infestations were entered into a GIS. Distribution maps were developed denoting the locations of infestations of these two weeds along the Rio Grande.